Regulating the Coordination Environment of Ruthenium Cluster Catalysts for the Alkaline Hydrogen Evolution Reaction.

Exploring high-efficiency catalysts for the electrochemical hydrogen evolution reaction (HER) in alkaline environments is attractive but remains challenging. Here we report a coordination regulation strategy to tune the atomic structure of Ru cluster catalysts supported on Ti3C2Tx MXene (Ru-Ti3C2Tx) for the HER. We identify that the coordination number (CN) of Ru-Ru could be slightly regulated from 2.1 to 2.8 by adjusting the synthesized temperature so as to achieve an optimal catalytic configuration. The Ru-Ti3C2Tx with a CNRu-Ru of 2.8 exhibits the best catalytic activity with a low overpotential of 96 mV at 10 mA cm-2 and a mass activity about 11.5 times greater than the commercial Pt/C catalyst. Density functional theory calculations demonstrated that the small Ru clusters have a stronger covalent interaction with Ti3C2Tx support leading to an optimal ΔGH* value. This work opens up a general avenue to modulate the coordination environment of catalysts for the HER.